I Don't Wanna Lose You
by dontworrybaby
Summary: Union Station with a different ending. -Marsan
1. I Don't Wanna Lose You

A/N: Could be a one shot, could have more chapters.. depends on whether anyone wants to read it. I know this has been done countless times with Marsan, but once I got the idea in my head, it wouldn't go away. This is the first fanfic I've ever written, and the only reason I'm posting it really is because I want some tips. I know this isn't the best, but I would appreciate it if you'd read it and review. Let me know if you want more, or if there's something I can improve on... Thanks!

**I DON'T WANNA LOSE YOU**

The cold Chicago wind stung his eyes and his skin as he ran through the city to find her.

_Her. Susan._

His best friend, his confidante, the one person he knew he could trust, and she was leaving. She was leaving him. He still couldn't believe he was running after her. He would never have done anything like this for Jenn. He loved Susan, and he was kicking himself for not telling her sooner. He'd only realised his feelings for her in the last couple of weeks, but it felt like he'd loved her forever. He was sure she loved him too, but if he didn't catch the train, he may never know.

He'd finally reached Union Station. He stepped out onto the platform, but he couldn't see her anywhere. He breathed out slowly, and he could feel the tears at the back of his throat as he realised he was too late.

"You lookin' for the chief?" Mark turned at the sound of a voice. There was a man walking passed him. Mark watched him. "They moved her to number six!" he called over his shoulder as he walked away. Mark turned around, looking to the next platform.

She was there. His breath caught in his throat and he could swear his heart stopped.

"Susan!" he yelled. She hadn't noticed him. He ran back out the door and onto the next platform. He called her name again and this time she turned to look at him. She raised her eyebrows in surprise.

"Mark?" she questioned as he moved closer to her. "You came to say goodbye?" a grin appeared on her lips.

"Stay." he shook his head. He was breathless after running so far. He was leaning against the train, clinging to it as though he would collapse if he were to let go. "I want you to stay."

Susan stared at him, stunned.

"What..?" was the only word she could find. "Mark…" she started, a frown appearing on her lips.

"Wait," he began, "… I love you.." he blurted it out, not wanting to tip-toe around the subject, they had done enough of that already. "I think I always have.. And I'm stupid for not saying it sooner…" he trailed off.

Her mouth opened slightly, she was surprised. She could feel the tears coming, but she wouldn't cry, not in front of him.

"Oh, Mark.." she said, trying to compose herself. "You have no idea how long I've waited for you to say that.." she confessed and a hopeful smile appeared on his lips. "But, I don't know if I can stay." she added sadly.

His smile disappeared.

"What?" he refused to believe what he was hearing.

She stood there, helpless.

"Susan," he started, "Right now I need you more than Susie does." he stopped, did she really need to hear this? "Chloe's happily married now, and she is Susie's mom. You need to accept that." he told her, and felt an ache in his heart at the hurt evident in her eyes.

Susan's eyes were brimming with tears now.

"Are you really asking me to choose between you and Susie?" she asked, a tinge of anger in her voice. Mark shook his head with a sigh.

"Susie doesn't need you like she did before.." he said, "You need to trust your sister to do the right thing now… and move on with your life."

Susan shook her head. She didn't want to believe what he was saying, but she knew he was right.

"I do love you." she said, desperately. "I really do. But I don't think I can move on from this."

"We can move on from this together, Susan. You have to trust me. I would never hurt you." Mark said, a small smile graced his lips. "Please, stay."

She stood there, trying to make her decision. "I don't want to lose you. We are perfect for each other." he said, practically begging now. "I know you feel the same."

Susan looked from Mark then back to the train again, before yelling to the man on the train: "Can you pass me my stuff please?"

She grabbed her luggage desperately, as the train pulled out of the station. Susan was breathing heavily as she looked at Mark. He had the goofiest grin on his face. He ran to her and wrapped his arms around her, he didn't want to ever let her go. He pulled away slowly, reaching one hand out to cup her face. His thumb stroked her cheek while his other hand found it's way to her hair, brushing it out of her face.

She exhaled slowly, relaxing at his touch. His lips found hers and they shared their first kiss.


	2. After The Kiss

A/N: Okay, first of all, thanks to everyone who read & reviewed! But I'm afraid this chapter isn't the best. I have a few ideas for storylines, it's just figuring out how to get to them that's the problem. haha. This chapter is fairly short too. I promise I'll get better!

**AFTER THE KISS**

Mark pulled away from the kiss slowly, still holding her face in his hands. He leaned forward, and pressed his forehead to hers gently.

"Thank you," he whispered.

Susan looked up at him. She bit her lower lip gently, knowing she couldn't hold in the tears much longer, but this time they were tears of joy.

"Thank _you_," she replied.

Mark noticed a tear roll down her cheek. Raising his hand, he wiped it away gently, before pulling her into a tight embrace. He wrapped his arms around her, and he never wanted to let go.

She buried her face in his chest. A small laugh escaped her lips.

Mark pulled away, looking at her curiously.

"What?" he asked, flashing her that crooked smile she loved.

"Nothing," she answered, still giggling softly. "I'm just happy." she stated, a grin spreading across her face. She looked into his eyes, smiling.

"Well I'm glad," he said, chuckling softly. "C'mon," he said, grabbing her suitcase. "Let's go back to mine.." he said, "I'm assuming you'll be moving back into your old place now?" he said, smiling happily.

"Ummm, yeah, I guess.." she replied, "It makes sense, considering you haven't moved your stuff over yet, and most of my stuff is still there.. That reminds me, I have to call Chloe." she frowned. "I can't believe we're doing this.." she almost whispered, letting a sigh escape her lips.

Mark stopped walking and turned to face her. He looked her right in the eye and said:

"Look, Susan, I know this is going to be hard. But I also know that we can do it. You've just gotta trust me and know that you're gonna be okay, 'cause I'm going to make sure you're okay... I'd do anything to make you happy." he said, seriously and completely genuinely.

Susan stared at him for a moment, clearly surprised by his sudden outburst.

"I know, Mark, I do trust you." she kissed him gently. "I'm just gonna miss Susie, that's all. I spent so much time thinking about leaving, and now I've suddenly changed my mind? I guess I'm still just a bit confused." she smiled reassuringly, and he nodded his head understandingly.

He pulled away again and took her hand in his. "I know, I know," he whispered soothingly.

They took the El to Mark's place and he opened the door to let her in.

She stepped inside and they stood there in an awkward silence. Susan shuffled from one foot to the other.

"Ummm, make yourself comfortable.. I'll be right back.." Mark said, realising he had a call to make. He stepped out of the room as Susan took a seat on the couch.

He dialled the familiar number.

"ER," he recognised Jerry's voice.

"Hey, Jerry," Mark said, "It's Mark. Is Doug there?"

"Yeah, he's right here, Dr. Greene." Mark waited.

"Hello? Mark?" Doug said.

"Hey, Doug.. Ummm, do you think you could cover for me today?" he asked.

"Uhhhh.. Sure, buddy. How did everything go?" he asked.

Mark didn't really want to talk to him about it now.

"Thanks, man... I'll talk to you later." he said.

"Awwww, c'mon!" Doug pleaded.

"Bye, Doug," Mark laughed softly and hung up the phone.

He went back into the living room.

"You want anything to drink?" he asked, smiling.

"Water would be good," Susan answered, a small smile gracing her lips. Mark went to the kitchen and soon returned with two glasses of water.

"Here you go," he said, joining her on the couch, he handed her a glass. More silence. They weren't used to this, and neither really knew what to say.

"I called Chloe.." Susan began. Mark looked up at the sound of her voice. "She seemed okay with it." she said, tracing her fingertip along the rim of her glass.

Mark slid closer to her. He stroked the back of her hand lightly with his fingers.

"Are you alright?" he asked her quietly. She nodded. He pressed his lips to her forehead gently, wrapping an arm around her shoulder. She leaned into him, closing her eyes. She exhaled slowly.

"Can I stay here tonight?" she asked, in a whisper.

"Sure," Mark said. "Of course you can."


	3. Back To Work

**A/N:** New chapter! Thanks to anyone that has been reading this story, and especially to those who review! You have no idea how much of a confidence booster that is! :)

Disclaimer: I'm afraid I do not own ER. Although I wish I did.

Mark awoke early the next morning, his neck stiff. He lifted his head slightly as memories of the night before came back to him. He smiled as he remembered how Susan had kissed him at the station. He looked down at her lying beside him on the couch where they had fallen asleep the night before. He closed his eyes again, burying his face in her neck. He could smell her shampoo, it was sweet. She stirred beside him. He looked down at her.

"Morning," she said groggily, opening her eyes. She turned in his arms, looking up at him.

"Morning," he said quietly, kissing her forehead softly. "Sleep well?"

"As well as you'd expect," she said, a smile playing on her lips. He allowed a soft chuckle to escape his lips.

He hugged her close to him, lightly stroking her right arm with his fingertips. He sighed contentedly.

"Don't you have to work?" she enquired, her face dropping slightly.

He groaned. "Do I have to?" he asked in a whiny, slightly childish voice.

She laughed at this. "As much as I would love it if you stayed here with me, I think you do," she answered, sarcasm clear in her voice.

"Ugh.." he sighed. He lifted his wrist to check his watch. It was 7:00am. He jumped up from the couch suddenly. "Crap!"

Susan sat up, she knew that look. "You're late?" she questioned, although she really didn't need to, it had happened to her enough times.

"I'm supposed to be at work in half an hour.." he said. "I have time to have a shower and I can get something to eat on the way there.." he said to himself mostly. Susan sat on the couch watching him. He flashed her a quick smile.

"I'm sorry I have to go," he apologised, kneeling down in front of her.

"It's okay," she reassured him.

He kissed her. Gently at first, growing more passionate, his lips moving with hers. She pulled away, laughing slightly.

"You should go get ready," she said, a grin spread across her face.

He nodded, getting up.

"There's a spare key on the counter.." he said, "You can stay here as long as you want." he left the room to have a shower. Susan got up from the couch.

And suddenly it hit her.

She had no job, and even if she managed to get her job back, what was she going to say to everyone at the hospital? She wasn't sure if telling everyone was the best idea, not until her and Mark had really talked about everything properly, at least. Maybe she could just tell them she got cold feet?

The water had stopped running in the shower and she heard the bathroom door open. Mark emerged from the room, dressed in his green scrubs. He threw his bag over his shoulder.

"Ummm, can I talk to you for a sec?" Susan asked him, standing up.

"Sure," Mark said, moving towards her. "What is it?"

"Well, would it be okay if we didn't tell everyone at work about us yet? I mean, not until we know what this is ourselves?" she asked, nervously.

"That's fine with me.." Mark replied, a little disappointed. He had sort of looked forward to telling everyone that they were an item. He loved her and he wanted everyone to know. But if this was what she wanted, then he was okay with it. "Does this mean you're going to come back to County?" he asked.

"I'm going to beg for my job back.. we'll see what happens. Don't worry about it." she kissed his lips lightly. "Now go, before you lose your job!" she laughed. He gave a her a quick smile and left his apartment.

Susan sighed, running a hand through her hair, which was a mess. She decided she would call Anspaugh today, sooner rather than later. She left Mark's apartment, locking the door behind her with the spare key he had left her. She got a cab to her place to have a shower and make a plan of action.

Mark had taken the El to work, as usual. He pushed through the doors at the entrance to the ER, and slipped into the lounge before Kerry Weaver could find him.

He was putting his jacket and his bag into his locker when he heard the door open behind him. He turned around to see Doug enter the lounge. Mark busied himself closing his locker and was about to leave when Doug stopped him.

"Mark," he said, "Are you gonna tell me what happened yesterday?" he asked, Mark couldn't read his expression. Mark avoided his eyes, knowing it was a bad idea to tell Doug, Dr. Intercom himself, but he was the one who had convinced Mark to chase Susan yesterday.

Mark pulled his gaze from the floor and a small, barely noticeable smile appeared on his lips. Doug knew what this meant immediately and a smirk played on his lips.

"Ah," he said, "That well?" he inquired, that signature Doug Ross grin spread across his face.

Mark nodded, bashfully. "Look," he said, "Please don't tell anyone. She doesn't want it to get out until we figure it out for ourselves."

"What's to figure out?" Doug countered. "You're perfect for each other!"

Mark nodded his head in agreement. "I know, but this is what she wants. And I'm okay with it." he said, "Although I would have loved to be able to brag.." he added, laughing softly.

Doug laughed. It had been a while since he had seen his friend so happy. Doug was glad he and Jenn had split up, he had never liked the way she thought she could control Mark, and he knew Susan was right for him. It made him think about Carol, he had really never stopped caring about her.

Mark noticed Doug had seemed to have lost interest in the conversation.

"You okay, Doug?" Mark asked, an eyebrow raised.

Doug looked up quickly. "Yeah," he said, plastering a fake smile onto his face, "I'm fine, just thinking.." he said, before grabbing his stethoscope from his locker and throwing it around his neck. "Well, I gotta go," he said, "Some of us have work to do." he joked. Flashing Mark a smile, he exited the lounge. Mark followed him quickly, anxious to get to work before Kerry could find him and give out to him for being late.

**Thanks for reading! The next chapter will probably be Susan trying to get her job back.. Will Doug tell everyone about them? Most likely. And then in future chapters it might get less happy, and follow some of the storylines from the actual show.. but you'll just have to wait and see.**

**Please r&r! I will **_love _**you forever! :)****  
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